JP4746474B2 - Alkaline detergent composition for steel sheet - Google Patents

Description

  TECHNICAL FIELD The present invention relates to an alkaline detergent composition for a steel sheet that is used particularly when electrolytically cleaning a steel sheet (steel strip) in an ironworks or the like.

  Degreasing and cleaning of the surface of a steel sheet is necessary as a pretreatment for performing surface treatment such as plating and painting together with pickling, and is a very large factor that determines the quality of a product. Examples of dirt attached to the surface of the steel sheet include esters such as beef tallow attached during cold rolling, rolling oil such as fatty acid and mineral oil, oil dirt such as rust preventive oil, and solid dirt such as iron powder. . Among these, especially when oil stains remain, gasification does not occur and volatilize in the furnace when annealing, and it remains as carbide on the steel plate surface, causing plating, uneven coating, and the like.

  The steel plate cleaning equipment is usually configured to continuously clean a steel plate (steel strip) wound in a coil shape, and is operated at a speed of about 30 to 1100 m / min. Accordingly, the cleaning time of the steel sheet is extremely short, at most several seconds. Cleaning is usually performed at a high temperature of about 80 ° C, and heating is performed using steam to keep the temperature constant, but steam costs are reduced by reducing the cleaning temperature without major modification of equipment. Is desired.

  On the other hand, in recent cold rolling of steel sheets, in order to improve mill cleanliness and productivity, cold rolling oil has been changed from beef tallow rolling oil to liquid synthetic ester rolling oil at room temperature. ing. Synthetic esters are not easily saponified by alkali and do not saponify into sodium soap in a short time, and therefore cannot be washed with conventional detergents. More recently, there is a tendency to increase the acid value of the rolling oil, but since the acid value has increased, a large amount of iron soap is generated after rolling, and the emulsifiability in the cleaning of the rolling oil is reduced, so that the detergency is reduced. There is also a problem.

In response to the above problems, a cleaning agent containing an alkali agent, polyoxyalkylene alkyl ether, and aldonic acids has been proposed (Patent Document 1). The cleaning agent of Patent Document 1 does not require addition of a physical cleaning method, increase in use concentration or cleaning time even at a low cleaning temperature of 50 ° C. or less, does not cause cleaning failure, and flows even at high concentrations. , Excellent storage stability and workability.
JP-A-11-222687

  However, the cleaning agent of Patent Document 1 is designed so that the cleaning property is good at a cleaning temperature of 50 ° C. or less, and even if it is used in a mode exceeding 50 ° C., only the cleaning property can be further improved. It wasn't. In addition, among the cleaning agents of Patent Document 1, those having improved cleaning properties when used in a mode exceeding 50 ° C. have large foaming and are not sufficient in terms of workability. In addition, when the cleaning temperature is set to 50 ° C. or lower with a conventional high-temperature cleaning facility, an additional cooling facility may be required.

  The present invention provides an alkaline detergent composition for a steel sheet that can clean and remove stains on a steel sheet at a cleaning temperature of 55 to 70 ° C. with good cleaning efficiency and that has low foaming and excellent workability. Objective.

That is, the present invention
An alkaline agent,
The following general formula (1): R—O— (EO) _a (PO) _b —H
(In the formula, R is a linear or branched alkyl group or alkenyl group having 12 to 14 carbon atoms, EO is an oxyethylene group, PO is an oxypropylene group, and the average added mole number a of EO is 11 to 15 and the average added mole number b of PO is 2.5 to 5). The alkali for steel sheet used at 55 to 70 ° C. containing at least one polyoxyalkylene alkyl ether represented by the formula (1) and aldonic acids. The present invention relates to a cleaning composition.

  Moreover, this invention relates to the method of wash | cleaning the stain | pollution | contamination adhering to a steel plate using the said alkaline cleaning composition for steel plates at the cleaning temperature of 55-70 degreeC.

  The alkaline detergent composition for a steel sheet of the present invention has good cleaning properties, no foaming, and good workability at a cleaning temperature of 55 to 70 ° C.

  ADVANTAGE OF THE INVENTION According to this invention, the washing | cleaning temperature of 55-70 degreeC can wash | clean and remove the stain | pollution | contamination of a steel plate efficiently, and the alkali-cleaner composition for steel plates excellent in workability | operativity is provided.

  As the alkali agent used in the present invention, any water-soluble alkali agent can be used. Specific examples include hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide, silicates such as sodium orthosilicate, sodium metasilicate and sodium sesquisilicate, phosphates such as trisodium phosphate, disodium carbonate And carbonates such as sodium hydrogen carbonate and dipotassium carbonate, and borate salts such as sodium borate. Two or more water-soluble alkaline agents may be combined. Sodium hydroxide, potassium hydroxide, sodium orthosilicate and sodium metasilicate are preferred, and sodium hydroxide and potassium hydroxide are more preferred.

  The polyoxyalkylene alkyl ether used in the present invention is represented by the above general formula (1). R in the formula is a linear or branched alkyl group or alkenyl group having 12 to 14 carbon atoms, and is preferably a straight chain. In addition, the addition form of an oxyethylene group and an oxypropylene group is the block body shown by the said General formula (1), and what added the block in this order is used suitably in this invention.

  The average addition mole number a of an oxyethylene group is 11-15, Preferably it is 11-14, More preferably, it is 11-13, More preferably, it is 12-13. The average added mole number b of the oxypropylene group is 2.5 to 5, preferably 2.5 to 4, more preferably 2.5 to 3.5, still more preferably 3 to 3.5. Among the polyoxyalkylene alkyl ethers, those represented by the general formula (1) in which the average addition mole number a of oxyethylene groups and the average addition mole number b of oxypropylene groups are within the above-mentioned range, At 55 to 70 ° C., the balance between the penetration of the cleaning agent and the emulsification is improved, and the detergency is improved. Moreover, the polyoxyalkylene alkyl ether represented by the general formula (1) has no foaming at a washing temperature of 55 to 70 ° C., and has good workability.

  In the present invention, it is considered that aldonic acids are used as chelates and act on the iron soap-derived soil to chelate iron ions, thereby facilitating dissolution of the soil using fatty acid soap. Aldonic acids are monosaccharides having a carboxyl group and alkali metal salts or amine salts thereof. Specific examples include glyceric acid, tetronic acid, pentonic acid, hexonic acid, heptonic acid and the like, and alkali metal salts or amine salts thereof. Preferred are gluconic acid, glucoheptonic acid and the like and alkali metal salts or amine salts thereof, more preferably sodium gluconate or sodium glucoheptonate. Aldonic acids can be used in combination of two or more.

  The alkaline detergent composition for steel sheet of the present invention is obtained by adding an optional additive to the alkaline agent, the polyoxyalkylene alkyl ether represented by the general formula (1) and the aldonic acids, and further blending a solvent. Prepared.

  The alkaline detergent composition for steel sheet according to the present invention has an alkaline agent content of 0.1 to 10% by weight, more preferably 0.5 to 8% by weight, from the viewpoint of ensuring cleanability at the time of steel plate washing. Preferably there is.

  The blending amount of the polyoxyalkylene alkyl ether represented by the general formula (1) is blended based on the alkali agent, and is preferably 0.005 to 5 parts by weight, more preferably 0 to 1 part by weight of the alkali agent. 0.01 to 0.5 part by weight, more preferably 0.05 to 0.1 part by weight. When it is 0.005 part by weight or more, the polyoxyalkylene alkyl ether is kept at a concentration necessary for cleaning the steel sheet. Further, when it is 5 parts by weight or less, the product stability in a concentrated product is good.

  The blending amount of the aldonic acids is blended on the basis of the alkali agent from the viewpoint of reducing stains derived from iron soap, and is preferably 0.005 to 5 parts by weight, more preferably 0.005 parts by weight with respect to 1 part by weight of the alkali agent. 01 to 0.5 parts by weight, more preferably 0.1 to 0.2 parts by weight.

  The alkaline detergent composition for steel sheets of the present invention is usually prepared as a concentrated product so as to be suitable during storage. As the solvent, water is usually used. As water used for the solvent of the composition of the present invention, deionized water is desirable. The concentration in the cleaning composition can be controlled by the solvent. The concentrated product can be further diluted with a solvent when cleaning the steel sheet. In addition, when cleaning the steel sheet, each component is pre-mixed in one or two liquids and may be diluted before use in the cleaning tank, and each component is put into the cleaning tank individually, It may be diluted with water.

  In the concentrated product, the total amount of the alkali agent, the polyoxyalkylene alkyl ether represented by the general formula (1) and the aldonic acids, an optional additive, and the composition using the balance as a solvent (preferably water) is used. As a standard, the blending amount of the alkaline agent in the composition is preferably 20 to 48% by weight, more preferably 30 to 45% by weight, further preferably 33 to 42% by weight, and further preferably 36 to 41% by weight. It is adjusted to become. When the content is 20% by weight or more, the amount of aldonic acids used as a stabilizer can be reduced, and the stability as a slurry is also preferable. Moreover, the viscosity of a cleaning agent is kept in the appropriate range on use as it is 48 weight% or less.

  In addition, in the alkaline detergent composition for a steel sheet relating to a concentrated product, the ratio of the polyoxyalkylene alkyl ether represented by the general formula (1) is 0.1 to 30% by weight, more preferably 0.2 to 20% by weight. %, More preferably 0.5 to 20% by weight. By setting the ratio of the concentrated product to 0.1% by weight or more, the concentration of polyoxyalkylene alkyl ether necessary for cleaning the steel sheet can be obtained. In addition, since this composition is stabilized in a slurry state, the product stability is improved by setting the ratio of the polyoxyalkylene alkyl ether having a low specific gravity to 30% by weight or less.

  Further, in the alkaline detergent composition for a steel sheet relating to a concentrated product, the ratio of aldonic acids is 0.05 to 20% by weight, more preferably 0.1 to 15% by weight, still more preferably 0.5 to 15% by weight. It is. By setting the ratio of the concentrated product to 0.05% by weight or more, the concentration of aldonic acids necessary for cleaning the steel sheet can be obtained. In addition, when the ratio of the concentrated product is 20% by weight or less, the amount of water necessary for dissolving aldonic acid can be reduced, and the necessary amount of alkaline agent necessary for product stabilization can be ensured.

  Moreover, water-soluble polymer carboxylic acids can be mix | blended with the high concentration alkali cleaning composition of this invention. In the case of blending water-soluble polymer carboxylic acids, the ratio is preferably 0.5 to 10% by weight, more preferably 1 to 8% by weight in the alkaline detergent composition for steel sheet relating to the concentrated product. Product stability can be secured by setting the ratio of the concentrated product to 0.5% by weight or more, and the viscosity of the cleaning agent can be appropriately controlled by setting the ratio to 10% by weight or less, so that the piping transportation of the cleaning agent can be secured. . Examples of the water-soluble polymer carboxylic acids include acrylic acid homopolymer (MW: 5,000 to 20,000), acrylic acid-maleic acid copolymer (MW: 5,000 to 20,000) and / or sodium thereof. Examples thereof include salts, and these are particularly preferably used in a proportion of 1 to 6% by weight.

  In the alkaline detergent composition for steel sheet of the present invention, an aromatic compound having 2 to 50 polar groups in one molecule can be used as a slurry stabilizer. Examples of the slurry stabilizer include a benzene derivative, a naphthalene derivative or an anthracene derivative which may have a substituent. By setting the number of polar groups to 2 or more, it is possible to suppress the cleaning liquid from gelling or destabilizing. In addition, by setting the number of polar groups to 50 or less, a stable cleaning agent can be obtained while maintaining the foam suppression effect. When the cleaning effect and the foam suppression effect are combined, the number of polar groups is particularly preferably 2-4.

The polar group is not particularly limited as long as it is not decomposed or hardly decomposed in an alkaline aqueous solution and exhibits a relatively strong hydrophilicity. For example, COOM, SO ₃ M, OSO ₃ M, One or more can be selected from the group consisting of NH ₂ , NO ₂ , NR ₁ H, NR ₂ R ₃ and OH. Here, M represents hydrogen, an alkali metal, an alkaline earth metal, an aliphatic amine having 1 to 4 carbon atoms, ammonia, or an alkanolamine, and R ₁ , R _2, and R ₃ are the same or different groups, Represents a linear or branched, saturated or unsaturated carboxylic acid group having 1 to 4 carbon atoms. In the present invention, among them, aromatic compounds containing COOM and SO ₃ M are preferably used.

  Specific examples of the slurry stabilizer include phthalic acid, isophthalic acid, terephthalic acid, sulfanilic acid, trimellitic acid, trimesic acid, 1,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, aminobenzoic acid, 1 , 5-naphthalenedisulfonic acid, 2,6-naphthalenedisulfonic acid, 2,7-naphthalenedisulfonic acid, 2-naphthol-6-sulfonic acid, 1,3,6-naphthalenetrisulfonic acid, 1,5-naphthalenediamine, For example, 2,6-dihydroxynaphthalene, β-naphthalenesulfonic acid formalin condensate, or a salt thereof. Preferred are isophthalic acid, terephthalic acid, 2,6-naphthalenedisulfonic acid, 2,7-naphthalenedisulfonic acid, 2,6-naphthalenedicarboxylic acid, and aminobenzoic acid.

  The slurry stabilizer has stable fluidity by uniformly dispersing alcohol, nonionic surfactant, anionic surfactant, amphoteric surfactant, mineral oil, etc., which are hardly soluble in alkaline aqueous solution, in high concentration alkaline aqueous solution. Allows the preparation of alkaline detergents. Therefore, since the blending amount of the hardly soluble drug in the high concentration alkaline aqueous solution can be dramatically increased as compared with the conventional uniform transparent type cleaning agent, a high concentration type cleaning agent can be prepared. .

  In the alkaline detergent composition for a steel sheet relating to the concentrated product of the present invention, when a slurry stabilizer is blended, the proportion is 0.1 to 20% by weight, preferably 0.3 to 5% by weight. By setting the content to 0.1% by weight or more, a stable cleaning composition can be obtained, and by setting the content to 20% by weight or less, the tendency of the cleaning agent to increase in viscosity or gel can be suppressed. As the slurry stabilizer, two or more aromatic compounds having the above polar group can be used in combination. Moreover, you may use together the aliphatic compound which has the same kind of polar group. The above-mentioned slurry stabilizer used in the present invention has an excellent slurry stabilizing action, but does not adversely affect the cleaning performance and foam suppression performance of the cleaning composition of the present invention. Have

  In diluting a concentrated product at the time of washing the steel sheet, the degree of dilution can be appropriately set, but the blending amount of the alkaline agent is 0.1 to 10% by weight, and further 0.5 to 8% by weight. It is preferable to dilute to

  Furthermore, the organic builder which improves the washability generally used for the alkaline detergent composition for steel sheets of the present invention, for example, alkali such as nitrilotriacetic acid, ethylenediaminetetraacetic acid, ethylenediaminediacetic acid, tetraethylenetetraminehexaacetic acid, etc. It is also possible to add additives such as aminocarboxylic acids such as metal salts or lower amine salts in consideration of COD and cost increase.

  The alkaline detergent composition for a steel sheet of the present invention has a good balance between the penetration and emulsification of the detergent at a washing temperature of 55 to 70 ° C., and stains adhering to the steel sheet can be washed and removed with good washing efficiency. The washing temperature is preferably 55 to 65 ° C. In addition, when the washing temperature is lowered, the penetrating power of the polyoxyalkylene alkyl ether represented by the general formula (1) is weakened. However, in the present invention, the washing temperature is set in a range of 55 ° C. or higher, thereby improving the washing property. You will be fully satisfied. Further, when the washing temperature is lowered and becomes lower than the cloud point of the polyoxyalkylene alkyl ether represented by the general formula (1), the detergent is bubbled even in the new solution, but the washing temperature is set to 55 ° C. or more. Therefore, foaming of the cleaning agent can be suppressed. On the other hand, when the cleaning temperature is increased, the polyoxyalkylene alkyl ether represented by the general formula (1) itself becomes oil droplets and remains on the steel sheet, resulting in a decrease in cleaning performance. The temperature is controlled to below ℃ and there is no deterioration in cleaning properties. In addition, when the washing temperature is increased, saponification of the contaminated ester oil proceeds, and it becomes easy to produce a large amount of fatty acid soap, but the washing temperature is controlled to 75 ° C. or less, and there is no problem due to the production of fatty acid soap. .

  The alkaline detergent composition for steel sheet of the present invention is effective when cleaning at a high line speed of 500 m / min or higher, and more effective when cleaning at a high line speed of 800 m / min or higher. In particular, it is effective when cleaning a cold-rolled steel sheet at a high speed of 1 second or less required for electrolytic cleaning. A general steel plate cleaning line has a structure of immersion cleaning → brush cleaning → electrolytic cleaning → brush cleaning → rinsing → drying, but the process from immersion cleaning to drying is about 50 m. When the line speed is 500 m / min, the entire process is performed. The cleaning is performed in an extremely short time of 6 seconds. Among them, the electrolytic cleaning process is about 10 to 20 m, and when the line speed is 500 m / min, the calculation is about 1.2 to 2.4 seconds. The alkaline detergent composition for steel sheet of the present invention is effective for electrolytic cleaning in such a short time or even in a shorter time, and thereby makes it possible to increase the cleaning line speed.

  Moreover, the alkaline detergent composition for steel sheet of the present invention is effective for a steel sheet to which a rolling oil containing 50% by weight or more of a synthetic ester adheres, and the rolling oil containing 70% by weight or more of a synthetic ester is used. It is more effective for the steel sheet to be adhered. Synthetic esters include, for example, synthetic esters derived from dimer acid or polymer acid of higher aliphatic unsaturated acids having 16 to 20 carbon atoms such as zomarinic acid, oleic acid, linoleic acid, gadoleic acid, tall oil fatty acid, propylene glycol, Polyhydric alcohols such as ethylene glycol, diethylene glycol, neopentyl glycol, butanediol, pentanediol, polyoxyethylene glycol, polyoxypropylene glycol, trimethylolpropane, pentaerythritol, glycerin and aliphatic carboxylic acids having 6 to 22 carbon atoms Synthetic ester used as raw material, synthetic ester made from aliphatic alcohol having 1 to 12 carbon atoms and aliphatic carboxylic acid having 6 to 22 carbon atoms, raw material made from polyhydric alcohol and aliphatic hydroxycarboxylic acid having 6 to 22 carbon atoms Synthetic D Tere, adipic acid, sebacic acid, azelaic acid, phthalic acid, trimellitic acid, polymellitic acid such as pyromellitic acid and synthetic esters using C1-12 aliphatic alcohol as raw materials, and ethylene oxide of the above alcohol, Examples include esters with propylene oxide and butylene oxide adducts.

  Furthermore, the alkaline detergent composition for steel sheet according to the present invention is effective for a steel sheet to which a rolling oil having an acid value of 10 KOH mg / g or more adheres, and the rolling oil having an acid value of 20 KOH mg / g or more. It is more effective for a steel plate to which is attached. The alkaline cleaning composition for cleaning steel sheets of the present invention is particularly effective for steel sheets containing a synthetic ester of 50% by weight or more and to which rolling oil having an acid value of 10 KOH mg / g or more adheres.

Moreover, the alkaline detergent composition for steel sheet of the present invention is effective for a steel sheet to which a rolling oil containing 10% by weight or more of a high viscosity ester having a viscosity at 40 ° C. of 70 mm ² / s or more adheres. It is more effective for a steel plate to which a rolling oil containing 20% by weight or more of a high viscosity ester adheres. In particular, this is effective for a steel sheet to which a rolling oil having a viscosity of 40 mm, preferably 100 mm ² / s or more, more preferably 150 mm ² / s or more is adhered. Examples of the high viscosity ester include synthetic esters made from the above dimer acid or polymer acid of a higher aliphatic unsaturated acid having 16 to 20 carbon atoms, the polyhydric alcohol and an aliphatic carboxylic acid having 6 to 22 carbon atoms. Examples include synthetic esters in which at least one hydroxyl group of the polyhydric alcohol is left as a raw material, and synthetic esters in which a polyhydric alcohol and an aliphatic hydroxycarboxylic acid having 6 to 22 carbon atoms are used as raw materials. Although not an ester, the alkaline detergent composition for steel sheets of the present invention is also effective for high viscosity compounds such as polybutene.

  Furthermore, the alkaline detergent composition for steel sheet of the present invention is effective for a steel sheet to which a rolling oil containing 1% by weight or more of a polymer of a higher aliphatic unsaturated acid having 16 to 20 carbon atoms adheres. . Examples of the polymer of higher aliphatic unsaturated acid include dimer acid and polymer acid of higher aliphatic unsaturated acid having 16 to 20 carbon atoms such as zomarinic acid, oleic acid, linoleic acid, gadoleic acid, tall oil fatty acid and the like. .

  The alkaline detergent composition for steel sheets of the present invention is used for continuous cleaning of steel sheets (steel strips) obtained by processing such as cold rolling in steel mills, that is, immersion cleaning, spray cleaning, brush cleaning, electrolytic cleaning, etc. The effect is exhibited, but the effect is great when used when electrolytically cleaning a cold-rolled steel sheet particularly at a low temperature.

<Steel plate cleaning test>
(1) Steel plate to be cleaned All steel plates to be cleaned were used by cutting a steel plate cold-rolled with a synthetic ester rolling oil into a size of 25 mm × 50 mm. The amount of oil adhering to the steel sheet to be cleaned used in this cleaning test is 100 mg / m ² .

(2) Preparation of pseudo-deteriorated cleaning solution 1% by weight of scum extracted oil obtained by extracting oil from a scum adhering to and deposited on a rolling mill with a solvent is added to the detergent composition, and the mixture is sufficiently stirred to simulate A deteriorated cleaning solution was prepared.

(3) Cleaning test In the cleaning composition (cleaning solution without dirt) and the pseudo-deteriorating cleaning solution, the center is equidistant from a pair of electrode plates each having a size of 100 mm in length and 50 mm in width (distance between the electrodes is 20 mm). The steel plate to be cleaned was immersed for 1 second, and then the steel plate potential was switched once from negative to positive at a current density of 10 A / dm ² , and each of the steel plates was subjected to electrolytic cleaning for 0.5 seconds, followed by electrolytic cleaning. Thereafter, the substrate was immersed and rinsed at 80 ° C. for 5 seconds and dried with warm air. As shown in Table 1, the temperature of the test cleaning liquid was 60 ° C. in the examples, and 60 ° C. or 40 ° C. in the comparative examples.

(4) Method for measuring the amount of residual adhered oil The amount of oil adhered to the steel sheet after washing and rinsing was measured using a steel sheet adhered oil amount measuring device EMIA-111 (manufactured by Horiba, Ltd.) for the cleaning solution without contamination and the pseudo-deteriorated cleaning solution. did. The measured value is an average value of five measurements. As the evaluation criteria for the cleaning property, the cleaning solution without dirt was evaluated as a new cleaning property, and the pseudo-cleaning cleaning solution was repeatedly evaluated as a cleaning property. That is, the evaluation of repeated cleaning performance was performed using a pseudo-deteriorated cleaning solution because the cleaning performance was evaluated when the oil adhered to the steel plate evaluation accumulated in the cleaning tank.

As a measurement standard for detergency, the amount of residual adhered oil after measurement was set as follows. New chemical cleaning resistance, residual adhesion oil amount after the measurement is passed is less than 20 mg / m ^2, and failed if 20 mg / m ² or more. The repeated washing resistance, residual adhesion oil amount after the measurement is passed is less than 30 mg / m ^2, and failed if 30 mg / m ² or more.

<Bubbling test>
A 1000 ml graduated cylinder was filled with 300 ml of cleaning liquid, and the temperature of the liquid was maintained at 60 ° C. in Examples and 60 ° C. or 40 ° C. in Comparative Examples as shown in Table 1. Thereafter, nitrogen was passed through the cleaning liquid at a rate of 1.0 L / min through a glass ball filter, and the cleaning liquid height and bubble height after 1 minute were evaluated. Evaluation was performed about new liquid foamability and stamina foamability. The stamina foaming property was determined by adding 0.05% by weight of lauric acid to the washing liquid in consideration of the saponification of the ester oil contained as a contaminant to form a fatty acid soap. In any of the evaluations, if the bubble height is less than 400 ml, “◎”, if it is 400 mm or more and less than 600 ml, “◯”, if it is 600 ml or more and less than 1000 ml, “△”, these were passed. The case where the bubble height was 1000 ml or more and overflowed the measuring cylinder was regarded as “x”, and this was rejected.

<Cloud point>
The cloud point was measured based on the cloud point measurement described in ASTM D2024. In a 150 ml beaker, weigh sodium hydroxide, polyoxyalkylene alkyl ether, sodium gluconate, and ion-exchanged water at 30 ° C. or less to a total amount of 100 g so that the proportions shown in the examples and comparative examples are obtained. Stir well until dissolved. Pour this solution into a 200 mm test tube to 50 ± 5 mL and place in a water bath. The test tube was taken out from the water bath when the white turbidity was clearly confirmed visually while stirring with a thermometer, and cooled with stirring slowly with a thermometer, and the temperature at which the solution became transparent was taken as the cloud point.

Example 1
2% by weight sodium hydroxide,
Polyoxyalkylene alkyl ether of general formula (1) (R is a mixture of linear alkyl groups having 12 to 14 carbon atoms, polyoxyethylene (average addition mole number is 12 moles), polyoxypropylene (average addition mole number is 3 Mol)) 0.2% by weight
Sodium gluconate 0.2% by weight,
And the cleaning composition which consists of remaining water (a balance amount uses deionized water) was prepared, and washing | cleaning evaluation and the foamability test were done on the washing | cleaning temperature conditions shown in Table 1.

Examples 2-4, Comparative Examples 1-9
A cleaning composition was prepared in the same manner as in Example 1 except that the polyoxyalkylene alkyl ether in Example 1 was changed to that shown in Table 1. Moreover, the washing | cleaning evaluation and the foamability test were done on the washing | cleaning temperature conditions shown in Table 1.

  From the results in Table 1, the cleaning compositions of Examples 1 to 4 contain the polyoxyalkylene alkyl ether represented by the general formula (1), and are used at a cleaning temperature of 55 to 70 ° C. Improves both liquid washability and repeated washability. On the other hand, in the polyoxyalkylene alkyl ether contained in the cleaning compositions of Comparative Examples 1 to 3, since the emulsifying power of the oil is reduced, repeated cleaning properties are reduced. Moreover, regarding foaming property, as for the cleaning composition of Examples 1-3, both new liquid foaming property and stamina foaming property are in a pass level. In particular, the detergent compositions of Examples 2 and 3 using a polyoxyalkylene alkyl ether represented by the general formula (1) having a long terminal propylene oxide chain exhibit high foam suppression properties. On the other hand, in Comparative Example 4 using a polyoxyalkylene alkyl ether having a short terminal propylene oxide chain, the stamina foaming property was unacceptable, and in Comparative Example 5 having no terminal propylene oxide chain, none of the foaming properties was found. It was a pass. Moreover, even if it was the same cleaning composition as Example 1, since the washing | cleaning temperature was 40 degrees C or less, since it wash | cleans below a cloud point, all foamability was a disqualified level. Since Comparative Examples 6 and 8 were washed below the cloud point, the foamability was unacceptable. Moreover, since the comparative example 7 did not add sodium aldonate, the oil adhering to the steel plate could hardly be removed.

Claims (2)

An alkaline agent,
The following general formula (1): R—O— (EO) _a (PO) _b —H
(In the formula, R is a linear alkyl group or alkenyl group having 12 to 14 carbon atoms, EO is an oxyethylene group, PO is an oxypropylene group, and the average added mole number a of EO is 11 to 15) , average addition mole number b of the PO Ri 2.5-5 der, oxyethylene group, addition form of oxypropylene groups, and at least one polyoxyalkylene alkyl ether represented by Ru block body der), An alkaline detergent composition for steel sheets used at 55 to 70 ° C., comprising aldonic acids.   A method for cleaning dirt adhering to a steel sheet using the alkaline cleaner composition for steel sheet according to claim 1 at a cleaning temperature of 55 to 70 ° C.